Lecture 4 Flashcards
Random error:
Due to chance e.g. individual biological variation, sampling error, measurement error
Systematic error:
Due to bias e.g. selection bias and measurement bias
Better than random error because you can work with it/find reason for
How to avoid error?
Standardisation, larger sample size, blind/double blind, calibration of equipment
Confounding:
Error due to the introduction of an external factor that may skew the data and demonstrate a non-existent event
Solutions = randomization, restriction & matching *
Reliability:
The degree to which a test is consistent and stable * in measuring what it is intended to measure
Validity:
The degree to which the test actually measures what it claims to measure
Obesity in adults ages 20-50yrs…
35% overweight, 21% obese*
Males (64%) were more likely to be overweight or obese than females (49%)
Australia’s future ‘fat bomb’…
72% of middle-aged males and 58% of middle-aged females are overweight or obese
approx. 1.5 million Australians are obese
estimated 700,000 will be hospitalized and 122,500 men and women will die of obesity related CVD within next 20yrs
conservative costing of $3 billion extra in health expenditure *
Body frame size is a way to…
Evaluate “normalcy” of body weight with standardized charts
Body frame size measurements:
Stature measured in cm
Biacromial diameter 9cm): distance b/w most lateral projection of the acromial processes
Bitochanteric diameter 9cm): distance b/w most lateral projection of greater trochanters
Body frame size limitations:
Data derived primarily from white populations *
Provide no assessment of body comp
Overweight:
A body weight that exceeds some avg for stature, and perhaps age, usually by some SD unit or % (frequently accompanies and increase in body fat, but not always)
Overfatness:
When body fat exceeds and age and/or gender appropriate avg by a predetermine amount
Obesity:
The overfat condition that accompanies a constellation of comorbidities
BMI =
Body mass (kg) / height (m squared)
BMI underweight =
<18.5 km/m2
BMI normal =
18.5-24.9
BMI overweight=
25.0-29.9
BMI obesity I =
30-34.9
BMI obesity II =
35-39.9
BMI obesity III
> /40
Problem w/ BMI =
Assumes r/ship b/w BMI and % body fat remains independent of age, gender, ethnicity & race
Doesn’t consider the body’s proportional composition or fat distribution
Factors other than excess body fat affect the numerator of the BMI equation
The possibility of misclassifying someone as overweight pertains particularly to athletes
Human body comp component model:
Two: fat mass, fat-free mass
Three: water, protein, fat
Four: water, protein, bone mineral, fat
Methods to assess body comp – direct measurement
person dead
- dissolve body in chemical solution to determine fat and fat-free components
- physically dissect fat, fat-free adipose tissue, muscle, bone